Air classifier



Feb. 26,4 192s. 1,660,664

A. H. STEBBINS AIR CLASSIFIER Filed Sept. 24. 1926 2 Sheets-Sheet l Elf] "@Hli zymmmmunu ATOfPA/EY Feb. 28, 1928.

A. H'. STEBBINS AR CLASSIFIER Filed Sept, 24, 1926 2 Sheets-Sheet. 2

liv

Patented Feb. 28, 1928.

incassi PA'fET OFFICE.

ALBERT IPI. *STEBBNEL 0F ANGELES, CALIFORNIA.

AIR CLASSIFER.

Application filed September 24,' w26. Serial No. 137,484.

This `invention relates to an air classifier and also to a series of similar classifiers arranged one above the other in stacked relation to subjectfthe materials to successive treatments. y

It is frequently desirable in the treatment of ores and other materials to eect the separation of very fine dust-like particles from slightly larger dust-like particles,4

but such minute particles are hard to classify due to their tendency to remain suspended in the air employed in effecting their classification, and also to the tendency of the smallest particles to cling to the larger particles.

When airis employed to effect a classil fication of these fine dust-like particles, a

Y complete classification of the particles cannot be effected bv a single air treatment, but it is necessary to subject the materials repeatedly to the action of slight air currents which will gently remove the finest particles froinkthe slightly larger particles.

The present invention therefore contemplates a multiple treatment classifier that consists of a 'number of similar classifying receptacles that are connected in series so that the heavier particles pass from one receptacle to another while some of the finer particles are removed from the larger particles in each receptacle.

One important feature of the presentin vention resides in the arrangement'of the classifying receptacles one-above the other are caused to move across a jet ofl air that serves to pick out the finer particles and carrythem upwardly in the receptacle.

Still another feature of the invention re sides in the construction whereby thematerials to be treated are delivered to the receptacle through a central yfeed pipe and the air is exhausted from the receptacle vnectioii with the accompanyingy vdrawings which illustrate invention.

In the drawingst Fig. l is a side elevation of a multiple treatment classifier constructed in accordance with the present invention;

Fig. 2 'on an enlarged scale vis asectional view taken on'the line 2-2 of Fig. l;

Fig. 3 on an enlarged scale is a vertical sectional view through two of the air classifiers of Fig. 1; l

Fig. 4 is a plan view of a spreader-supporting element to be described; gig. 5 is a bottomview ofthe spreader; an

Fig. 6 is a vertical sectional yview of a modified construction for admitting air into the lower portion of a classifying receptacle.

The multiple treatmentclassifier is shown inFifr. 'l as formed of a number of individual' classifying receptacles 10 which are disposed'one above the other in stacked relation so that the heavier particles being treated will flow5 under the influenceiof good practical 'forms of the gravity, from one receptacle to the next'for Y cal portion 12 and a downwardly,extendingl conical portion 13. The upper conical portion 12 of each receptacle is provided with an opening4 lll through which air is eX- hausted from the receptacle and the downwardly extending conical portion 13 of each receptacle is provided withzan opening; l5 through which the heavier materials are discharged.

An important feature nef the present inare directedalgainst ajet or annular blade of' air entering the lower portion of the receptacle, and which serves to remove the lighter particles from the heavier particles and to carry these lighter particles upwardly. within the receptacle.

In-the construction shown the rising air iio conical wall 18 of the casing lies in spaced relation to the lower vend of the conical portion 13 of the next upper receptacle of the stack, to forni the annular' air passage 16, as will be apparent from Fig. 3. The .adjacent receptacles 10V may be supported in spaced relation one .above the other-by thev braces ,19 or by any other .suitable supporting structure, and the lower end portion 13 of each receptacle is supported centrally within the upper portion of a Ycasing 17 by the spacing elements 2O .shown in Fig. 2.

Each annular .casing 17 is provided with a feed pipe 121 which extends downwardly some distance into the interior of a Yreceptacle 10 to vdeliver ithe materials to be treated into the same from .the next upper receptacle, and the diameter of this feedfpipe V21 is such that the annular air passage 14 is formed between .this pipe and the opening kin the upper end Vof the conical portion 12 of each receptacle. Each annular casing 17 is connected to vthe exhaust conduit 22 iby a pipe 23 extending from Yits casing 17 Ato the exhaust conduit. The conduit 22 preferably increases in diameter in an upward `direction to accommodate the .increased volume of air passing Athrough the upper portion of Ithe conduit and the upper end of the conduit :22

may be connected to an exhaust fan 24, the blast discharge outlet of which fan is connected to a dust extractor 25 by the pipe 25a. The construction of the cannular Lcasing'17 and associated parts just described lis :such that air is drawn upwardly within .each receptacle 10 around the feed pipe 21 and through the annular opening 14 at the upper end of each receptacle, as indicated ,by the arrows. c

As a resu-lt of this construction rising air currents are produced entirely around the feed pipe 21. The suction produced i-n each receptacle 10 by the means just described serves to draw air .from the atmosphere in wardly through the annular opening 16 at the lower end lof each receptacle, and the heavier materials which pass downwardly within a receptacle in opposition to the rising air currents will settle upon the inclined walls 13 of the receptacle and as they slide kdown these inclined walls they will be directed against the blade of air entering the passage 16. rllhis will serve .to disengage from the larger particles the line particles which tend to cling .to such larger particles and will serve to carry upwardly within the rod 27 the upper end of which is connected.

`to a three-way spider 28 mounted within the feed pipe 21. The construction of the spreader 26 is such that materials falling `upon the same will be directed .outwardly within the receptacle by the inclined walls -Vof the spreader. It may be desirable to provide air currents flowing upwardly around the lower end of -th-e spreader 26. These air currents will ser-ve to disseminate the particles that tend to cling together, and such air currents may conveniently be produced by mounting a disk 29 within the lower end kof the .spreader 26 so that an annular .air passage 30 is provided between the inner wall of the spreader and the-edge of such disk. One Vor more pipes 31 Vwhich serve to conduct air from the Vatmosphere to the interior of the spreader may be provided, yand as a result the suction produced within a receptacle 10 will draw air from the atmosphere through the pipes-31 into the spreader .26 and this air will escape through the annular slot 30 to produce the desired iair currents ar-ound the base of the spreader.

In some cases it-may be desirable to introduce air at the lower end of a receptacle `through .two or more annular passages, as 4shown Iin the modification of Fig. 6; this Aconstruction may be desirable since several `jets or blades of air will separate the tinev particles from the larger particles ymore eff-ectively than would a single blade. The modified constructionshown in Fig. 6 differs from that shown in Fig. 3 only in that the distance between the lower yend of ivtlie conical wall 13 ofthe receptacle land the adjacent conical wall 18 of the yair exhaust casing is increased, and in the space thus formed are supported one or more conical shaped rings-32 which serve to form the sev- :eral kair passages 33.

From the foregoing description when read in connection with the drawings, it will be seen that any desired number of classifying receptacles 10 may be supported one above the other in stacked relation so that the heavier materials pass successively through .the different receptacles, and that these heavier particles are subjected in each receptacle to rising air currents which will remove some of the lighter particles from the Sil Sill

,lill

heavier particles and carry these lighter partlcles up through the upper end, of the receptacle and into the suction conduit 22. 'lhe heaviest particles which through the entire series of receptacles l() are discharged large number of receptaclcsril() will not beexcessive because the individual receptacles neednot be large, and the strength ofair employed` in each receptacle will be relatively weak, due to the necessity of employing extremely gentle forces in effecting the classification of fine dust-like particle. By supporting the receptacle in stacked relationnas shown, and by 'connecting each relce 'itacle with the exhaust conduit 22 `an i Ide- Sired number of individual receptacles may be operated fronia single exhaust pipe, and

`may be supplied with materials from a single feed pipe. Furthermore, by subjecting the larger particlestiine and time again to the action of slight rising aircurrents, the finest particles are gradually removed from the slightly larger particles.l

What is claimed is l. An air classifier, comprising',` in conibination, a receptacle having an air inlet opening adjacent its lower end, means for delivering the materials to be treated into the upper part of the receptacle, ahollow spreader supported within the casing below the feed means and having sloping side walls to deiect outwardly the falling particles, means for exhausting air from the upper portion of the receptacle, and a pipe leading from the exterior of the receptacle into the interior of the spreader and adapted to produce air currents around the lower edge of the spreader to diffuse the particles.

2. An air classifier, comprising in combination, a receptacle having an air inlet opening adjacent its lower end, means for delivering the materials to be treated into the upper part of the receptacle, means for exhausting air from the upper portion of the receptacle, a hollow spreader supported within the casing below the feed means and and having sloping side walls to deflect outwardly the falling particles, a pipe leading from the exterior of the receptacle into the interior of the spreader and through which air is drawn by said exhaust means to produce air currents around the lower end of the spreader to diffuse the particles.

3. A multiple treatment classifier, coinprising in combination, a series of classifying receptacle-s arranged one above the other in compact relation and each having a feed pipe that extends from its lower end into the next receptacle to direct the heavier particles from one receptacle intothc next, means for admitting air into the lower portion of each receatacle, means constructed to form a narrow annular discharge passage at the upper end of each receptacle about the feed pipe that projects into the saine, and a suction pipe leading from the upper portion of each receptacle to 4exhaust air therefrom through. said annular passage. v

A multipleV treatment classifier, coinprising in combination` a series of classifying receptacles, arrluiged one above the other in compact relation and each having a feed pipe that extends Vfrom its lower end into the next receptacle todirect the heavier ,par-

ticles from one receptacle into the next,

means for admittingair into the lower portion of each receptacle, an annular casing' formed at the upper end of each receptacle about Vthe feed pipe for that receptacle and constructed to provide a narrow annular air passage about the pipe and through which air is exhausted from the receptacle, and a suction pipe for exhausting air from `each of said casings.

5. fr multiple treatment classifier, coinprising in combination, a seriesof'classifying receptacles arranged one above the other in stacked relation and each having` a feed pipe that extends from its lower end into the next receptacle to direct the heavier particles from one receptacle into the next, means for admitting air into the lower p0rtion of each receptacle, an exhaust casing provided at the upper end of each receptacle for exhausting' air from the receptacle about the feed pipe projecting into the saine, an

exhaust conduit disposed along side the stack ofy receptacles, and a connection between each casing and said conduit.

6. An air classifier, comprising, in combination, a receptacle having an enlarged body portion and a protrudiim` conical upper end in which a central opening is formed, a material feed pipe extending through said opening into the receptacle, an annular cas'- ing connected to the upper end of the receptacle and Isurrounding said pipe, means for introducing air into the lower portieri of the receptacle, means positioned at one side of said easing for exhausting air therefrom, and said upper converging end of the receptacle being constructed to extend inwardly into close proximity to the outer walls of the feed pipe to form a restricted throat about said pipe that leads from the receptacle to the casing and which is given a size to equalize the lstrength of the air entering the casing at different points around the feed pipe.

7. An air classifier, comprising in combination, a reeeptacle'having an enlarged central portion and reduced converging end portions, a feed pipe extending into the uplill) per end of the receptacle, `means Jfor introducing air into the lower vportion of the receptacle to pass upwardly through the falling` materials, an annular air exhaust casing' provided at the upper end of the receptacle about the ieed pipe and connected to the receptacle by a reduced neck that forms a restricted passage between the receptacle and casing` and means for exhausting' air from the casing to draw air lupwardly through the receptacle.

8. A multiple treatment classifier, coinprising in combination, a stack formed of a large number of small classifying' receptacles each having,` a bulged central portion and oppositely extending converging end portions, means 'for supporting' the receptacles in stacked relation with the lower end of one receptacle extending' into the upper end of the next and arranged to admit air from the atmosphere into the lower. end of each receptacle, an air exhaust casing at the upper end of each receptacle, a conduit extending` lengthwise of said stack, and means Jfor exhausting' air from each casing to draw air upwardly through the receptacles and including branch pipes leading from the casings to said conduit.

9. A multiple treatment classifier, comprising in combination, a stack formed of lreceptacle and connected thereto by a reduced neck, and means for exhausting air from each of said casings to draw air upwardly through the receptacles.

10. A multiple treatment classiier, comprising in combination, a stack of classifying receptacles each formed with reduced end portions and a bulged central portion, means for supporting the receptacles in stacked relation so that the heavier particles will flow by gravity from one receptacle to the next, means for introducing air into the lower portion of each receptacle, an air exhaust casing provided at the upper end of each receptacle and connected thereto by a neck, and means orexhausting air from each of the' casings to draw air upwardly through the receptacles.

In testimony whereof, I have signed my name to this specification.

ALBERT H. STEBBNS. 

